Craniotomies are surgical procedures performed in the treatment of various brain problems, such as tumors, aneurysms, blood clots, head injuries, abscesses, and the like. During a craniotomy procedure, access to the brain is achieved by the creation of a hole in the bone that defines the skull. The hole or “window” in the skull is usually created by identifying the area of the brain to which access is needed, drilling several holes into the skull near the periphery of this area, inserting a cutting tool into one of the holes, and making cuts from one hole to another. Removing the cut-out area of the skull, generally referred to as a bone flap, allows the desired access to the brain.
If all of the drilled holes are joined by cuts, such that the cuts form a complete outline of the “window”, then the bone flap can simply be removed. Alternatively, if the cuts form only a partial outline of the window, the bone flap can be bent out of the way, in a hinge-like manner. Although the size and shape of the bone flap will vary with the desired cranial access area and size, a typical bone flap would be generally rectangular in shape and approximately four by six centimeters.
After the desired medical or surgical procedure on the brain has been performed, the bone flap must be replaced and held in a stable position to allow the skull to heal. There are many methods available for affixing the bone flap to the skull. One general method, for example, requires drilling pairs of holes in the edges of the skull and bone flap, threading wire through the holes, and twisting or tying the ends of the wire together to secure the edges of the bone flap to the skull. Disadvantages of this method include the tedious nature and length of time required for the procedure and the possibility of injury from drilling the holes too deep or from the sharp ends of the wires.
Another method of fixation generally involves the use of bone plates which are secured across the gaps between the bone flap and skull by screws. The disadvantages associated with the use of plates and screws relate to the undesirable cosmetic appearance resulting from the protrusion of the plate and screw above the bone surface. As there is minimal intervening soft tissue between the skull and the skin, unappealing external appearance is particularly a problem. The lack of soft tissue also has the unwanted consequence of permitting the patient to feel the plate and screw simply by pressing on the scalp. Thus, there is a need for improved devices for fixing a bone flap to a skull.